Graft copolymers have attracted attention in many fields over the past few decades. See Hadjichristidis et al., Graft Copolymers, in Encyclopedia of Polymer Science and Technology, ed. A. Seidel, John Wiley & Sons, Hoboken, N.J., 2004, Vol. 6, page 348; and Cowie, Block and Graft Copolymers, in Comprehensive Polymer Science, ed., G. Allen and J. C. Bevington, Pergamon, Oxford, 1989, Vol. 3, p. 33. Compared to block copolymers, graft copolymers can provide additional architectural flexibility, since graft (side chain) density, graft length, and backbone length can be systematically varied. See Hadjichristidis et al., Graft Copolymers, in Encyclopedia of Polymer Science and Technology, ed. A. Seidel, John Wiley & Sons, Hoboken, N.J., 2004, Vol. 6, page 348; Cowie, Block and Graft Copolymers, in Comprehensive Polymer Science, ed., G. Allen and J. C. Bevington, Pergamon, Oxford, 1989, Vol. 3, p. 33; and Hadjichristidis et al., Prog. Polym. Sci., 2006, 31, 1068. By choice of monomers and by controlling the macromolecular composition and architecture, the resulting graft copolymers can find a range of applications, including as water-dispersible nanostructures with the potential to carry drugs and other biological cargo, as nanostructured materials, as photonic materials, and as tough renewable materials. See Hadjichristidis et al., Graft Copolymers, in Encyclopedia of Polymer Science and Technology, ed. A. Seidel, John Wiley & Sons, Hoboken, N.J., 2004, Vol. 6, page 348; Cowie, Block and Graft Copolymers, in Comprehensive Polymer Science, ed., G. Allen and J. C. Bevington, Pergamon, Oxford, 1989, Vol. 3, p. 33; Gamlish et al., Polymer Chemistry, 2012, 3, 1510; Feng et al., Chemical Society Reviews, 2011, 40, 1282; and Theryo et al., Macromolecules, 2010, 43, 7394. However, there remains a need in the art for additional synthetic methods for making multigraft copolymers, including methods that involve less stringent reaction conditions, that are compatible with the use of lower cost initiators, and/or that are compatible with a wider range of dispersing media, including water. There is also a need for addition synthetic methods that can result in the preparation of graft copolymers with high molecular weights and/or a large number of side chains, as well as methods that are more compatible with large scale polymer preparation.